As a production process of a toner for electrostatic image development (which hereinafter may be simply referred to as a “toner”), a polymerization method has such advantages that, as compared to a grinding method and the like, the energy required for the production is small, a toner can be miniaturized in particle size, and generation of fine components can be suppressed.
As the polymerization method, a suspension polymerization method, an emulsion aggregation method, and the like are known. Especially, an emulsion aggregation method, is preferably adopted since a shape can be easily controlled.
The emulsion aggregation, method includes an aggregating step followed by an aggregation terminating step. In the aggregating step, fine particles of a binder resin produced by an emulsion polymerization, and the like, and other toner components such as fine particles of a colorant are aggregated using an aggregating agent. In the aggregation terminating step, the aggregation of the fine particles of the binder resin is terminated using an aggregation terminating agent. As the aggregating agent and the aggregation terminating agent used in the aggregating step and the aggregation terminating step, metal salts and the like are generally used (see Patent Literature 1).
However, when metal, salts are used as the aggregating agent or the aggregation terminating agent, the metal elements derived from the metal salts come to be remained in the aggregated particles. Since a compound containing such metal elements has sometimes high hygroscopicity, the resultant toner also has high hygroscopicity in such a case. As a result, a charge amount of the toner is varied depending on a certain environmental condition of image forming processing, and thus a problem arises that image defects occur. Specifically, when printing is performed in a large amount under a high-temperature and high-humidity environment, image defects such as fogging and image density reduction are caused.